The invention relates to a device for program selection, for selecting a program to be carried out by an apparatus on a group of successive samples. The program may typically be a measuring program, for instance for measuring beta or gamma activity of samples.
It is frequently necessary to perform a number of processing or measuring operations which are similar, but not entirely identical, on a large number of samples successively brought by a conveyor to a working station (or a number of working stations operated in parallel). Frequently, the samples may be associated in "groups," the samples in a given group being subjected to exactly the same operations whereas samples belonging to different groups do not undergo the same processing steps. An example of such a situation is the determination of the beta activity of successive samples by liquid scintillation spectrometry. In this case, activities of samples belonging to different groups are frequently measured using different counting parameters (energy selection window, duration of counting, standardization curve, etc). Other examples are the preparation of liquid samples by combustion and absorption, e.g. using the process described in French Pat. No. EN 70 36 644 (Intertechnique) and the determination of gamma activity of samples, using a scintillation crystal.
Prior art devices have been employed for selecting a program to be carried out on the successive samples of a group. Such a device is described in U.S. Pat. No. 3,749,916 and French Pat. Specification No. 1,552,274 (Intertechnique). That device, for selecting a program to be carried out on a number of successive samples disposed in a conveyor which brings them to a working station, comprises a marker which is associated with the group and moved along with the group by a link conveyor. The marker is coded with the address of the program in an auxiliary store (for instance a teletype punched tape) and causes the addressed program to be transferred to a main store where it is kept during the entire processing of the samples of the group. This solution is quite flexible but does require a programming operation necessitating a qualified operator and in addition does not provide a permanent program support which is directly and visually readable by an operator.
Other prior art systems use "wired" programs; the front panel of the apparatus comprises banks of switches or potentiometers in number equal to the number of groups between which the samples may be divided, and the most important parameters of the processes can be displayed in each bank by means of the switches and potentiometers. As before, the wired program is selected by a marker associated with the group. A system of this kind is expensive if the number of groups required and the number or parameters to be programmed are large; no permanent record is available.